The broad objective of this proposal is to compare the pharmacological, physiological and biochemical status of vascular smooth muscle from normotensive and hypertensive animals (rat, rabbit, dog). Vascular smooth muscle from normotensive and hypertensive animals will be compared with respect to: a) Their reactivity to various endogenous spasmogens (e.g., angiotensin II, norepinephrine, K ion, etc.) and vasodilators (e.g., adenosine). Precise measurements of force per cross-sectional area (i.e., Newtons/sq. m) will be used to minimize artifacts due to the well known changes in the vessel wall seen in chronic hypertensive states. b) The utilization, compartmentalization and biochemical handling of Ca ions. This will include evaluation of electromechanical and pharmacomechanical utilization of intracellular and extracellular Ca ion pools, uptake and release of Ca ions from isolated sarcoplasmic reticulum and Ca ion requirements for purified actomyosin ATPase. Phosphorylation of myosin in isolated proteins and intact strips will also be evaluated. c) The relationship of cell energetics to contractile activity. This will include studies on O2 sensitivity of normotensive and hypertensive smooth muscle. d) Mechanical studies to determine if the physical and geometric properties of the vasculature or the smooth muscle cells are altered in the hypertensive state.